Every now and then a physician performs a procedure that simply does not have its own CPT code. This happens more often than beginners expect — especially with newer surgical techniques, experimental procedures, and highly specialized services. In these situations, coders use unlisted procedure codes. Knowing when and how to use them correctly is important for both the CPC exam and real-world coding practice.
What Is an Unlisted Procedure Code?
An unlisted procedure code is a CPT code used when no specific code accurately describes the service that was performed. Every section of the CPT codebook includes one or more unlisted codes — generic catch-all codes that say in effect “a procedure was performed in this area that does not have its own specific code.” Unlisted codes typically end in 99 and include phrases like “unlisted procedure” or “unlisted service” in their descriptions.
When Is It Appropriate to Use an Unlisted Code?
Use an unlisted procedure code when all of the following are true:
- No existing Category I CPT code accurately describes the procedure performed
- No Category III code exists for the procedure (Category III codes take priority over unlisted codes)
- The procedure is documented in the medical record and was actually performed
- The service is not already bundled into another code being reported
Common Unlisted Codes by Section
| Section | Unlisted Code | Description |
|---|---|---|
| Evaluation & Management | 99499 | Unlisted evaluation and management service |
| Surgery — Integumentary | 17999 | Unlisted procedure, skin, mucous membrane and subcutaneous tissue |
| Surgery — Musculoskeletal | 27899 | Unlisted procedure, leg or ankle |
| Surgery — Cardiovascular | 37799 | Unlisted procedure, vascular surgery |
| Surgery — Digestive | 49999 | Unlisted procedure, abdomen, peritoneum and omentum |
| Radiology | 76497 | Unlisted computed tomography procedure |
| Pathology | 89240 | Unlisted miscellaneous pathology test |
| Medicine | 99199 | Unlisted special service, procedure or report |
| Anesthesia | 01999 | Unlisted anesthesia procedure |
Documentation Requirements for Unlisted Codes
Because unlisted codes have no set fee in payer fee schedules, claims submitted with unlisted codes require special documentation. Most payers require a special report to accompany the claim explaining exactly what was done and why no standard code applies. This report should include:
- A detailed description of the procedure performed
- The reason the procedure was performed and the diagnosis
- The time, effort, and equipment required
- An explanation of why no existing CPT code adequately describes the service
- A suggested fee with justification — often based on comparison to a similar procedure
Without adequate documentation, claims with unlisted codes are almost always denied. The payer needs enough information to price the service appropriately since there is no standard fee schedule amount for unlisted codes.
Category III Codes vs Unlisted Codes
This is a critical distinction that is frequently tested on the CPC exam. Category III codes (marked with the letter T) are temporary codes for emerging technologies and new procedures. The rule is clear: if a Category III code exists for a procedure, you must use it instead of an unlisted code. Using an unlisted code when a Category III code exists is incorrect coding.
The reason for this rule is data collection. CMS and the AMA track Category III code utilization to decide whether procedures should be promoted to permanent Category I status. If coders bypass Category III codes in favor of unlisted codes, this data collection is undermined.
How Payers Handle Unlisted Code Claims
When a payer receives a claim with an unlisted code, they typically require manual review by a medical reviewer or claims examiner. This means unlisted code claims take longer to process and are more likely to be sent back for additional information. Payment is determined on a case-by-case basis, often by comparing the service to a similar existing procedure.